Field of the Invention
The present invention relates to an image forming optical system, an image pickup apparatus, an optical apparatus, and a capsule endoscope.
Description of the Related Art
As an optical system having a wide angle of view that forms a curved image, a wide-angle lens described in International Unexamined Patent Application Publication No. 2012/090729 is available. The wide-angle lens described in International Unexamined Patent Application Publication No. 2012/090729 includes in order from an object side, a first lens, a second lens, and a third lens. The first lens is a meniscus lens having a convex surface directed toward the object side, the second lens has a positive refractive power, and the third lens has a concave surface directed toward an image side.